Fingerprint sensors that measure the fingerprint pattern using electric field sensing methods and capacitive sensing methods have become well established. U.S. Pat. Nos. 5,940,526 and 5,963,679 are examples of this type of fingerprint sensor, the entire contents of which are incorporated herein by reference. These systems measure the fingerprint pattern by generating an electric field between the finger and the sensor array, and measuring the spatial fluctuations in field strength at the sensor array caused by the shape of the fingerprint ridge and valley pattern.
In some recent applications, it may be desirable to capture images of fingerprint patterns from fingers that are farther away from the sensor array than is typical with today's technologies. Unfortunately, as the finger gets farther away from the sensor array, for example when a relatively thick dielectric lies between the sensor array and the finger, the relatively thick dielectric between the sensor array and the finger may cause variations in the electric field between the finger and the sensor array. These variations may cause image data generated by the finger sensor to be representative of a blurred image.